Sound absorbing material



Nov. 17, 1931. J. H. NASH SOUND ABSORBING MATERIAL Filed June 11. 1959 WM 2 w A p I A TTORNEY Patented Nov. 17', 1931 UNITED STATES PATENT OFFICE JOSEPH H. NASH, OF NARBERTH, PENNSYLVANIA, ASSIGNOR TO J'OHNS-MANVILLE CORPORATION, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK SOUND ABSORBING EATERIAL Application filed we 11,

This invention relates to improvements in sound-absorbing materials adapted to be used in buildings, enclosures and the like.

One of the primary-objects of the invention is to provide rooms and enclosures with a sound-absorbing material which is not only highly effective for deadening of sounds, but also neat and attractive in appearance.

A further object is to provide a sound absorbing material with a fire-resisting surface or facing in such a manner as not to diminish its sound-absorbing capacity.

Another object of the invention is to provide sound-absorbing materials with porous facings having permanent colors, which can readily take various tints or shades to give them a pleasing finished effect.

A further object of my invention is to provide an acoustic composition having the desirable sound-absorbing properties of various fibrous materials combined with the advantages with respect to durability and appearance of plastic or stone-like materials.

A still further object of the invention is to provide a sound-absorbing wall, ceiling or the like which has a suitable backing or support to which sound-absorbing material of a resilient nature is attached, with a coating or layer over said material that is non-combustible, yet sufiiciently porous to allow sound waves to freely pass through it into said material. to be damped and deadened; and of such character also that it can be painted or otherwise colored and decorated as may be as desired.

For sound-absorbing or acoustic purposes, felt is of superior excellence, and its use has therefore become quite extensive in this field. It is advisable, however,to provide the felt with an exterior coating to increase its durability and improve its appearance, but in the attachment of this coating various difiiculties have been encountered. When cloth or some other fibrous material is utilized to I cover the felt, the looks may be improved,

1929. Serial No. 870,013.

and the sound-absorbing properties of the felt are effectively preserved; but the partition is not rendered fireproof; and when plas tic or liquid coatings are employed, it is found that they tend to crack, especially where pieces of felt come together, and to become hard and brittle, becoming unsightly and screening the felt to such an extent that the sound waves cannot penetrate it. The chief end and aim of the whole construction is thus sacrificed.

The defects are overcome in the practice of my invention by the provision of a protective coating for the felt or similar sound-absorbing material comprising a relatively thin layer or coating of granular material having numerous openings which permit the passage of sound therethrough into the sound-absorb ing material. The granules are preferably of substantially the same size and consist of material adapted to protect and impart a decorative effect to the sound-absorbing material. Mineral material, which term is intended to include hard, non-combustible material having or capable of taking a decorative finish, is especially suitable for the practice of my invention. The granular particles are preferably secured in position with respect to each other and the sound-absorbing material by a suitable binder, so that no blocking results of. the sound-transmitting openings through the protective layer. Various other features and advantages of my invention will be apparent from the following detailed description of an example thereof taken in connection with the accompanying drawings, wherein:

Figure 1 is a perspective view showing the construction of an acoustic composit-ion'according to this invention.

Fig. 2 is an enlarged detail thereof in section. and Fig. 3 is a similar detail of a modification. Numeral 1 indicates a backing or support for the acoustical composition comprislng an interior layer 2 of a porous, resilient, elastic or non-rigid sound-absorbing material preferably fibrous in structure, 'such as felt, and an exterior protective layer or coating 3 of granular material having numerous openings therein to permit the passage of sound therethrough into the sound-absorbing material.

The exterior layer of granular material is very thin relative to the interior layer of sound-absorbing material, and in general it is desirable to make the exterior layer as thin as is compatible with its decorative and protective function. For instance, as shown in the drawing, the depth of this coating may approximate the diameter of the individual granules, and in general, this coating need not consist of more than a few layers of granules in'order to attain the best results. The thinness of this coating prevents it from absorbing any substantial amount of sound, and this function is accomplished practically entirely by the porous resilient interior layer 2. The screen-like construction of the layer 3, however, serves to break or mutilates the sound waves impinging thereon into numerous small ones which are more readily absorbed by the sound-absorbing layer and in this respect serves to increase the acoustical efiiciency of the composition.

The individual granules are preferably of about the same size, such as may be obtained by suitable screening of aggregates of indiscriminate sizes. Granules of the same dimensions have a maximum amount of voids or openings therebetween when packed, and by using granules of this character, the coating 3 is provided with the maximum amount of sound-transmitting openings. For this reason, rounded particles are preferable to virregular ones, and I' have found rounded particles of pumice particularly advantageous. t

The size of the individual granules may vary, but obviously excessively large or small anules should not be used. Granules varymg in size from about 1/64th inch to 1/8th inch in average dimension have been found to be suitabl Various methods may be utilized for ap plying the protective layer 3 of granular ma terial to the sound-absorbing material 2.

The granular material or aggregate may be fixed to the layer 2 with a suitable binder which may be applied directly to the felt or other Soundmbsorbing material and the age ate sprayed or blown into place; or the in er may be mixed with the aggregate and the mixture spread or trowelled on to the felt surface. The binder used, in addition to havin the requisite adhesive properties, shoul be waterproof and of such a character that it will shrink upon drying so as to produce a minimum amount of'blockin'g of the openings between the aggregate, thereby leaving the granules and sound-absorbing layer bound to a large extent only at their points or areas of contact. While various binders may be used, I have found casein glue, and a binder containing a pyroxylin base such as is used in the leather industry, particularly suitable.

An advantageous modification of my invention is shown in Fig. 3, wherein a screen 4, preferably of a suitable metal, such as copper or galvanized iron, is combined with the protective layer 5. The mesh of this screen should be such that the granules will not pass entirely therethrough, but is of such a size that a large proportion of the granules may pass partly through or become embedded therein. The screen may be stretched over the surface of the sound-absorbing material and the mixture of binder and aggregate applied thereto and trowelled into place, or the aggregate may be applied by stretching the screen on a frame and then adding the aggregate. lVhen made by the latter method, the reinforced screen may be made and marketed separately from the sound-absorbing felt or like material, and assembled therewith upon the construction of the acoustical wall or partition. A loosely woven fabric or netting may be substituted for the metal screen to advantage under some conditions.

My acoustical composition may be either in tile form, or it may be built up or fabricated directly on the wall, ceiling or other surface.

When a tile is to be produced, the felt may be applied to a rigid backing 1 of any suitable material, then the aggregate is applied by one of the methods above described and the sheet of material cut into blocks or tiles of suitable size which may be applied by. nailing or cementing into place. This method of manufacturing my product has the distinct and highly important advantage that all operations are carried out in the "1.0- tory, where conditions may be accurately controlled.

In forming my product directly on the wall or ceiling, the felt is attached to the surface thereof and the granular coating formed as in the construction of the tile. No backing is necessary in such cases or is furnished by the wall or ceiling structure.

Felt, especially reinforced felt, such as punched felt, has been found to be particularly adapted for use according to my invention; however, various other resilient sound-absorbing materials may be substituted therefor, as, for example, fibrous materials such as balsamwool, rock wool, fibre board and fabrics. A loosely woven fabric or netting may be applied to the felt or other sound-absorbing material to give additional Ill reenforcement before application of the 5 through into the sound-absorbingmaterial.

tective coating 3 may consist of any of a wide variety of hard crushed materials. Pumice and tufa, .and various other mineral substances, have been found to be suitable for this purpose. The granular material selected may have a natural decorative tint, or such a tint may be imparted to it by painting or dyeing either before'or after its application,

,to the sound-absorbing surface. When the granular material is tinted after being applied to the sound-absorbing surface, the coloring material employed should preferably be a light bodied paint or lacquer which will not unduly reduce the porosity of the coating. A certain amount of the coloring matter will soak into the sound-absorbing material, but a sufficient amount will remain on the granular particles to impart the desired color. By proper selection of coating material, a great many different decorative effects can be obtained. The resulting composition has the distinct advantage of simulating stone and ceramic acoustical structures in its appearance and durability,lboth as .to wear and fireproof qualities, but possesses sound-absorbing properties much greater than such structures.

What I claim is z.

.1. An acoustical construction comprising a sound-absorptive layer of porous resilientsound-absorbing material provided .with a relatively thin exterior protective layer upon which the sound waves impinge of granular particles having numerous openings therebetween to mutilate the sound waves and permit the passage of'sound therethrough into the sound-absorbing material. r 1

2. An acoustical construction comprising a sound-absorptive layer of felt. sound-absorbing material provided with a relatively thin exterior protective layer upon -which the .sound waves impinge of granular particles having numerous openings therebetween to mutilate the sound waves and permit the passage of sound therethrough into the sound- -absorbing material. 3. An acoustical construction comprising a sound-absorptive layer of fibrous sound-absorbing material provided with a relatively thin exterior protective layer uponwhich the sound waves impinge of granular particles bonded to each other and having numerous openings therebetween to mutilate the sound waves and permit the passage of sound there- 4. An acoustical construction comprising a sound-absorptive layer of porous resilient sound-absorbing material having bonded thereto a relatively thin exterior protective.

5. An acoustical construction comprising a.

sound-absorptive layer of porous resilient sound-absorbing material provided with a relatively thin exterior protective layer upon rial bonded to each other only at their points of contact. a v I 6. An acoustical construction comprising an interior layer of porous resilient soundabsorbing material, a relatively thin exterior protective layer upon which the sound waves impinge of incombustible mineral material comprising granular pumice having numerous openings therein to permit the passage of sound therethrough into the soundabsorbing material, and a bonding material to secure the protective layer to the soundabsorbing material.

7 An acoustical construction comprising an interior sound-absorptive layer of soundabsorbing felt, a relatively thin exterior protective layer upon which the sound waves impinge of granular particles having numerous openings therebetween to permit the passage of sound therethrough into the soundsabsorbing material, and abonding material adhesively securing the protective casein glue binding the protective layer of.

granular particles to the sound-absorbing material only at the points of contact.

9. An acoustical construction comprising an interior sound-absorptive layer of fibrous sound-absorbing material, a relatively thin exterior protective layer upon which the sound waves impinge of substantially equally sized granular particles of mineral material,

and a bonding material binding the protective 5 layer on the sound-absorbing material and of a character adapted to shrink sufliciently on drying to prevent blocking of the openings between said particles.

10. An acoustical construction comprising an interior sound-absorptive layer of porous resilient sound-absorbing material,iand a relatlvely thin exterior protective layer upon wh ch the sound waves impinge comprising a meshedelement having incombustible granular particles embedded in the apertures there- 'ofso as to permit the passage of sound therethrough into the sound-absorbing material. 11. A protective screen for sound-absorb ing surfaces comprising a meshed element having incombustible granular particles embedded in the apertures thereof so as to permit the passage therethrough of substantially all of the sound impinging thereon.

12. An acoustical construction comprising an interior sound-absorptive layer of porous resilient sound-absorbing material, and a relatively thin exterior protective layer upon which the sound waves impinge. comprising a metallic meshed sheet having a coatlng secured thereto of incombustible mineral material having numerous openings therein to permit the passage of sound therethrough into the sound-absorbing material.

Signed at New York, in the county of New York and State of New York, this 10th day of June, A. D. 1929. C

JOSEPH H. NASH. 

